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Field Trip Part 1: CNR Rao Circle Underpass

On January 5, B.CLIP students went on a site visit to the CNR Rao underpass near IISc. Mr. B N Vishwanath, an independent auditor at the JNNURM, walked the students through how infrastructure projects are conceptualised, and why they often fail or get delayed.

This project sits on an arterial path in Bangalore, and it was planned with the aim to ease vehicular congestion and facilitate easy movement of traffic between Mekhri circle, Malleshwaram and Yeshwantpur. The underpass leads on one side to National Highway 4 which links 20 districts of Karnataka.

This is a project taken up under the national Jawaharlal Nehru National Urban Renewal Mission (JNNURM) scheme and was sanctioned as a turnkey project in early 2008 at the cost of about 30 crores. Stipulated to be completed in 10 months, it is now fast approaching 60 months since project start. With many months and years of inactivity, there is breakneck progress in the work over the past three months and the underpass is set for full use in the next few weeks.

On the 5th of January, 2014, B.CLIP students went on a site visit to the CNR Rao circle underpass near IISc. Mr. B N Vishwanath, an independent auditor at the JNNURM, walked the students through how an infrastructure project is conceptualized, and why they often fail or get delayed.

This is one of 59 turnkey projects in Karnataka, and due to faulty planning, 50% were completed with time overrun, while the rest have not been completed yet.

Details of the project have been mentioned here.

This underpass was planned to release vehicular congestion and facilitate easy movement of traffic between Mekhri circle, Malleshwaram and Yeshwantpur. The road from Maramma circle to Yeshwantpur leads to NH4, and links 20 districts of Karnataka.

To cater to the volume of traffic, this underpass was designed to be 100ft wide – 4 lane, bidirectional, and signal-free – road. The underpass has been designed as a single vent with no wall dividing the roads. The concrete roads enable a maximum vehicular speed of 60 kmph.

The walls on either side of the road had an RCC structure that had to have a constant height of 10m from the ground level. Therefore, in the construction of the underpass, to retain such a height, 30-40 ft had to be excavated to provide a foundation, and enable concreting, steel-setting and curing. Concrete was used on these roads instead of asphalt as it provides high durability and can last for over 30 years.

These retaining walls have weep-holes with filter material that enable water to seep out of the walls, and release pressure on it. This water percolates into a narrow drain on either side of the underpass, and flows into the lowest point.

From there, it goes into a main drain pipe that flows into a natural valley. The closest natural valley to this is 350m away. To prevent back-flow, the main pipe is laid at an angle. A chamber is also provided, and with the pipe being 1m in diameter, it is convenient for people to walk into it and maintain it, and ensure it remains debris-free.

To minimize accidents, a crash barrier has been constructed that has been said to reduce the intensity of an impact by 30%.

A 28m span and heavy beams have been erected across the width of the road to provide structural integrity to the overpass, instead of having a wall in between the roads. Grips had to be installed to allow free movement of traffic and concreting above, and each girdle weighs about a tonne.

Only after excavation started did they identify utilities that had to be rerouted. The water supply line to IISc, the fiber optic cables, BWSSB trunk sewer, Ground Level Service Reservoir (GLSR), and others were all cutting across the width of the underpass.

Unfortunately, more land was required to construct pavements on either side of the roads – a constraint still faced today.

This project was sanctioned in early 2008, and was stipulated to be completed in 10 months from then. The project, however, got inexorably delayed, and progress was slow.

Mr. B S Prahlad (right, in blue), Executive Engineer with BBMP, is one of the key personnel to turn this project around and expedite its progress. The underpass is expected to be fully functional in the forthcoming weeks.

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